Collected on this day...

Redbud is sure to catch your eye in the spring! The picture above of redbud (Cercis canadensis) in bloom was taken yesterday at Schenley Park. Below illustrates how advanced leaf out was last spring (specimen on right), compared to 1915 (specimen on left: flowers, no leaves yet).

I love stumbling upon specimens collected from the same site. These two specimens of blue-eyed Mary (Collinsia verna) were collected by two different collectors on April 28th along Chartiers Creek near Pittsburgh, PA. But they were collected 74 years apart: Thomas C. Porter in 1871 and again by Carnegie Museum curator Otto Jennings in 1945. I doubt recollecting on the same calendar day, same site was intentional. Having duplicate specimens collected from the same site and from the same location decades apart makes the herbarium all the more powerful to measure biological change through time, including population size, morphology (size/shape differences) and other traits, and genetic changes.

Blue-eyed Mary (Collinsia verna) is a beautiful plant, with deep blue colored petals that give it is quirky name. It is a winter annual, meaning it germinates in the fall/early winter and blooms in the spring, produces seeds, and process repeats. It is not very common in Pennsylvania anymore and is tracked as rare in Pennsylvania. It can be found across the central and eastern United States in damp, rich woods and especially in valleys and slopes in floodplains along creeks. Seeing a population of blue-eyed Mary can be breathtaking in spring – with flowers carpeting the forest floor as far as the eye can see.

Expect more "recollected on this day" posts. Last year, we botanists initiated a long term "recollection" project at the Carnegie Museum of Natural History where we are revisiting sites across western Pennsylvania on the same calendar day as former plant collectors to compare current plants to those of our historic specimens. We are focusing on sites where collections are particularly strong -- southwestern Pennsylvania. Many of these sites are now state parks, roadsides, or have been developed as residential areas and/or have been transformed by human activities altogether.

Some results from the first year of this project can be found in the new We Are Nature: Living in the Anthropocene exhibition at the museum. These specimen recollections will grow the plant collection at the museum in a way to maximize future research. For instance, we can compare phenology (for example, flowering times) and how they might be affected from a century of climate change. We are also documenting introduced and invasive species which were absent from these sites 20, 50, or 100+ years ago, as well as native species which may no longer be locally present or abundant. More results to come!

And, who knows how scientists 20, 50, or 100+ years will use these specimens.

Below is a sampling of some recollections from April 27, 2017 in Fox Chapel, Pennsylvania (near Pittsburgh). Note the striking differences in stages of flowering development between 1900 and 2017. The specimens on the left were collected by the first curator of botany at the museum, John Shafer.

Spring leaf out is a bit “behind” in Pittsburgh this year. Well, for Norway maple in Schenley Park compared to 1948. Plant leaf out and flowering times is variable for many species each year due to differences in spring temperatures. This Norway maple specimen was collected by Botany curator Otto Jennings. Norway maple (Acer platanoides) is commonly planted across our region, common as a street tree or park plantings. Norway maple is invasive in Pennsylvania, spreading into natural habitats. Its leaves superficially resemble the well known sugar maple but has a different leaf shape. ﻿Norway maple has even been put on the Canadian 20 dollar bill instead of the native sugar maple (http://www.cbc.ca/news/canada/ottawa/canada-s-new-20-bill-at-centre-of-maple-leaf-flap-1.1343767).﻿ A good way to tell it is Norway maple is that exudes a white latex from the leaf when picked.

Keep an eye out for Norway maple over the next week! That light yellow/green you see at the tips of trees (especially along highways) in early spring is not tree leaves, but flowers. And many of these trees in urban areas around Pittsburgh are Norway maple. Many trees flower early in the spring, before they leaf out. Many tree species are primarily wind pollinated, so flowering before most species leaf out facilitates pollen to blow around with fewer obstructions.

In a long-term project initiated last year, we are recollecting specimens on the same calendar date and in the same location as historic specimens in the herbarium. These recollections will grow the herbarium with future use in mind – permitting comparisons across time, such as changes in leaf out dates, flowering, and genetic works. Long term studies (and herbarium specimens) are important to understand the effects of climate change and other human activities because of yearly variation. Check back for more on this project!

Image below: Norway maple buds today on a tree in Schenley Park, Pittsburgh (Apr 4, 2018). It is not quite ready to go. Note the buds are swollen but are not yet burst. Compare this to the specimen collected in 1948, in full flower and early stages of leaf expansion.